Controlling circuits for rotary connector switches



C. E. LOMAX July 18, 1950 CONTROLLING CIRCUITS FOR ROTARY CONNECTOR SWITCHES 2 SheetsSheet 1 Filed July 22, 1947 $6 Iwnvmwhmm INVENTOR. CLARENCE E. LOMAX ATTOR EY C. E. LOMAX July 18, 1950' CONTROLLING CIRCUITS FOR ROTARY CONNECTOR SWITCHES 2 Sheets-Sheet 2 Filed July 22, 1947 IMKNNN AI mhm r mum INVENTOR. CLARENCE E. LOMAX ATTORNEY Patented July 18, 1950 CONTROLLING CIRCUITS FOR ROTARY CONNECTOR SWITCHES Clarence E. Lomax, Chicago, Ill., assignor to Antomatic Electric Laboratories, Inc., Chicago, 111.,

a corporation of Delaware Application July 22, 1947, Serial No. 762,620

11 Claims.

The present invention relates to automatic or semi-automatic telephone systems and more particularly concerns improvements in the circuits of switches known as rotary connectors.

The rotary connector of this invention has access to groups of lines extending to private branch exchanges, and it may also have access to individual lines. When the usual directory number is dialed for calling a private branch exchange, the connector completes the call over the first idle line encountered in the group for 'the'exchange. To obtain the night service feature which permits any line of a group to be tested in the same manner as an individual line, aspecial number is dialed.

An object of the invention is to prevent the loss of calls due to slow answering. Circuits in the connector switch control an alarm for notifying the maintainer at the telephone office that a call has not been answered promptly. Although the calling subscriber may abandon the call, the wipers of the connector still engage contacts of the seized line to indicate to the maintainer the line on which the delay occurred and to render the line busy to other connectors."

Afeature of the invention is the means for rendering ineffective the function for automatically selecting an idle line of a group. When the wipers stop at a particular set of contacts that are common to one or more groups of lines, a relay operates for preventingautomatic rotary motion. One more digit is dialed to advance the wipers to the desired line.

Another feature is an improved circuit arrangement for preventing automatic rotary motion when all lines of a group are busy.

Other features of the invention, attained by combining a stepping sequence switch of the type having cam discs with a Strowger switch, will become apparent from the complete description of the invention. a

Figure 1 and Figure 2 together show a rotary connector and representative line equipment associated with the lines accessible at the connector banks. At the left in Figure 1 the sequence switch SEQ includes stepping magnet SM, and spring combinations actuated by cam discs CI to Cl inclusive. The driving mechanism is so arranged that upon deenergization of magnet -SM the seven cam discs are rotated to the next one of nine positions.

The well known Strowger switch includes the vertical stepping magnet at the lower left of Figure l, the rotary stepping magnet at the lower right of Figure 1, the release magnet ELSE, the

vertical off-normal springs VON, and in Figure 2 four wipers 213 to 216. Each wiper has access to ten levels of contacts, eleven contacts per level.

. Four different ways of connecting the control and extra control contacts of each contact bank set are illustrated at B in Figure 2. At the first set of four contacts, the extra control contact 211 is connected permanently to ground potential; the control contact 286 and also the corresponding line contacts are not connected. When a calling subscriber causes thewipers to rotate to this set, the circuit for relay I In in Figure 1 is completed at contact 211. Upon operating, relay H0 cancels the automatic rotary function and prepares circuits for advancing the wipers in response to the dialing of an additional digit. After relay H0 operates, automatic rotary is cancelled for any line appearing in that level operated to this set when this line is busy and any other line of the group is idle, control contact 218 and extra control contact 219 are at ground po-.-

tential. When the wipers encounter ground on both control contacts, busy relay operates over the circuit completed at wiper 215 and bank contacts 278 to transfer the circuit that includes the extra control wiper 216 from relay H0 to stepping relay 90. Shortly thereafter, relays 50 and 10 release to complete a circuit including contact 279 for relay-90. Relay 9E! closes a circuit to energize the rotary magnet ROT for advancing the wipers to thenext set. However, if all the lines of the group are busy, the extra control contact 219 is not at ground potential, because in each of the multiple circuits that con- .nect contact 218 with contact 219, either the contacts corresponding to 234 of a line relay or 264 of a cut-off relay are open. Therefore, if there is not an idle line when the wipers reach the group, the wipers remain on the first line while the connector returns a busy signal to the calling subscriber.

Contacts 2l3 of line relay 2H! and contacts 242 of cut-01f relay 240 are not required for operation of'the circuit as described but are 3 shown to make the relays of the first line of the group similar to the relays of the other lines. Uniformity facilitates wiring and maintenance.

The circuits for an intermediate trunk line of a group are shown at the third set of contacts. Control contacts 286 and extra control contacts 28I are connected by a link 281. When this line tests busy after the wipers are stepped to this set from the second set of contacts, both contacts are at ground potential, and the wipers are ad= vanced to the next set.

The last line of the group, or an individual line, is connected as indicated at the fourth set of contacts. If the lines that were idle when the con-- nector reached the group become bus y while the connector is searching, the wipers will stop at the last line. The circuit for stepping relay 90 is open at the extra control contact 283 and the circuit of the busy relay is complete t ground at thecontrol contacts 282.

The sequence switch SEQ controls circuits required for operating the Strow'ger switch, prepares line circuits, and in response to ground pulses which occur at fixed intervals sounds an alarm to indicate to a maintainer that a call has not been answered within a determined interval after the ringing current has been connected. Relay l deenergizes at the completion of each series of impulses dialed by a calling subscriber to advance the cam discs to the next position. In position I a circuit is prepared for the vertical stepping magnet VERT; in position 2 a circuit is prepared for the rotary stepping magnet ROT; in position 3, if a special number for night service has been dialed, another circuit is prepared for the rotary stepping magnet, or for usual service 'a self-interrupting circuit of magnet SM is prepared for advancing the cams; in position 4 ground potential is placed on the control conductor for operating the cut-off relay in the line circuits of the called subscriber; in position 5 the called subscribers line is connected to the ringing generator, and a circuit is completed fo energizing the sequence magnet SM at fixed intervals; positions 6 and 'I' are for timing; in position 8 the circuit for advancing the cams is opened, and a circuit is completed to an alarm for notifying a maintainer that answering has been delayed. If a call is completed after the cams reach position 8, a circuit of the alarm is opened, and a circuit is closed for advancing the cams to position 9. The cams return to position I after the Strowger switch has been released.

A complete understanding of the invention may be had from the detailed description now given. The subscribers sub-station and the automatic switches preceding the connector may be the well known type associated with automatic Strowger switches. When the connector is idle, negative potential is extended to control contacts in the banks of the preceding selectors over the following circuit: negative battery, resistor R at the lower left of Figure 1, contacts I2I, contacts I3, contacts 36, and control conductor C to the bank contacts.

When a preceding switch seizes the connector of Figure 1, pulsing relay operates over the following circuit: ground, lower winding of relay 20, contacts I4, line H, through the pre ceding switches and the subscribers telephone, line I8, contacts II, upper winding of relay 20, and negative battery. At contacts 2| the circuit is completed from ground, through the winding of slow release relay 30 to negative battery. Relay 30 operates, at contacts 34 returns ground over conductor C to the preceding switch, at contacts 32 prepares the pulsing circuit for the vertical magnet, and at contacts 3| closes the circuit for slave relay 40. Relay 40 operates. At contacts 4| a circuit is prepared for grounding control wiper 215; at contacts 42 a circuit is prepared for relay H0 which at times prevents automatic trunk hunting; at contacts 43 a looking circuit is prepared for relay H0; at contacts 44 a circuit is prepared for maintaining relay 40 energized after the loss of a call due to slow answering; at contacts 45 a circuit is prepared for ring cut-off relay at contacts 46 a circuit is prepared for extending pulses of ground potential to the stepping magnet of the sequence switch; at contacts 4'! and 48 an incomplete ground circuit is transferred from the release magnet to an alarm conductor SUPY. 2; at contacts 49 a circuit is prepared for grounding one side of the called subscribers line during ringing; at contacts 35 a locking ground circuit is prepared; and at contacts 36 negative battery is disconnected from the incoming control conduc tor C.

When the calling subscriber dials a digit following the seizure of the connector, pulsing relay 2U responds to the series of interruptions to cause vertical stepping. The pulsing circuit controlled by relay 20 may be traced as follows: ground, contacts 22, contacts 32, contacts l33, contacts I22, winding of vertical magnet VERT, and negative battery. Slow releasing relay 10 is operated on the first pulse over the circuit including ground, contacts 22, contacts 33, contacts I33, winding of relay 1i), and negative battery. At contacts 'II a point is opened in the connection to the extra control conductor EC; at contacts 13 an additional point is opened in the control circuit C; and at contacts 12 the circuit including ground, contacts 12, winding of sequence stepping magnet SM, and negative battery, is closed to energize the magnet. The shaft and wipers 213 to 216 inclusive are raised to the level corresponding to the digit dialed. In response to the first vertical step the vertical offnormal spring VON is actuated to transfer an incomplete circuit from the magnet SM to the release magnet RLSE. Shortly after the completion of the series of impulses relay I9 releases to open the energizing circuit of stepping magnet S 1.

Upon releasing SM causes the cams of the sequence switch SEQ to step to position 2. Cam CI at contacts I20 prepares a homing circuit for the sequence switch, at contacts I2I opens a further point in the control circuit C, and at contacts I22 opens the circuit of the vertical stepping magnet VERT. Cam C2 at contacts I23 connects the rotary magnet to the pulsing circuit and at contacts I24 closes the circuit including ground, contacts I24, winding of slowreleasing relay 56, and negative battery. Relay 58 operates. At contacts ill a control circuit for automatic rotary is prepared; at contacts 52 a point is opened in an incomplete circuit to the sequence stepping magnet; and at contacts 53 a circuit is prepared for busy relay 60.

The next digit that is dialed is the final digit except when the night service feature is to be effective. Relay 20 pulses to operate relay 10 again and to rotate wipers 273 to 276 inclusive to the desired contact in the switch bank. The

"circuit for energizing the rotary stepping magnet includes ground, contacts 22, contacts 32,

contacts I33,contacts I23, winding of the rotary magnet EDT and negative battery.

If the wipers engage line and control contacts corresponding to the first line of a group in which the first line is busy, but in which one or more lines are idle, the wipers 215 and 216 will encounter ground potential on contact 218 and contact 219 respectively. The busy relay 50 operates over the following circuit: ground on conductor CF, contacts 24 I, contacts 2 I2, contact 218, wiper 215, contacts 53, winding of relay 60, and negative battery. At contacts 6|, ground is disconnected from the incomplete circuit to test wiper 215; at contacts 62 a point is opened in an incomplete circuit of relay H; at contacts 63 a circuit is prepared for stepping relay 90; at contacts 64 an additional point is opened in a circuit to the sequence stepping magnet; at contacts 65 a locking circuit is prepared; and at contacts 65 busysignal is connected through condenser 91 to the calling subscriber's line. Although the busy signal is connected to the calling subscribers line when the first line of a group tests busy, the connector will quickly select automatically an idle line if it is available within the group, and-relay 60 will immediately release to disconnect the busy signal before the calling subscriber recognizes it. Shortly after the completion of dialing, relay'lil releases to open the circuit of the sequence switch magnet at contacts 12 and to close the circuit of stepping relay 90 at contacts 1|. Upon deenergizing the sequence switch magnet SM advances the cams to position 3. Cam G2 at contacts I23 disconnects the rotarymagnet from the pulsing circuit controlled by relay 20, and at contacts I 24 opens the circuit of slow-releasing relay 50. Cam C5 at contacts I33 disconnects relay from the pulsing circuit. Cam 06 at contacts I34 prepares a circuit for operating the stepping magnet of the sequence switch, and at contacts I35 prepares a circuit for the rotary magnet. The operating circuit for relay 95 may be traced from the ground for busying control contact'218 through contacts such as 234 and 254 associated with an idle line, extra control contact 219, wiper 216, contacts I 31, contacts III, contacts 42, contacts 1|, contacts 53, contacts 5!, interrupter springs 21, and winding of relay 95 to negative battery. Relay 9!) at contacts SI closes its inter-locking circuit. including ground, contacts 35, contacts 9I, interrupter springs 21, winding of relay 90 and negative battery, at contacts 92 closes an obvious circuit to maintain slow releasing relay 50 operated, and also at contacts 92 closes the following circuit for energizing the rotary magnet ROT: ground, contacts 92, contacts I35, winding of rotary magnet, and negative battery. Upon operating the rotary magnet advances the wipers to the bank'contacts of the next line of the group, and at interrupter contacts 21 opens the circuit of stepping relay 90 which then releases to open the circuit of'the rotary magnet at contacts 92. If this line is busy stepping relay 90 will operate again over the previously traced circuit which extends from the ground potential at the extra control contact. The alternate of the groupfthe operating circuit of relay 5!? and rotary magnet ROT remains open at contacts 92. Relay 50 releases. At contacts 52 a locking circuit for busy relay B0 is completed from ground, contacts 35, contacts 65,contacts 54, and winding of relay 50 to negative battery, and at contacts 5I the circuit of relay 9Ilis opened at an additional point. ing. the busy signal that was connected to the line at contacts 66 of busy relay 60, the calling subscriber replaces his receiver upon the switch hook whereupon relay 20 deenergizes and opens the circuit of slow release relay 30 at contacts 2|. Relay 35 at contacts 3| opens the circuit of relay 40, at contacts 34 removes the ground from control conductor C to release the preceding switches, and at contacts 33 prepares a circuit for the release magnet. Upon releasing relay 4!) at contacts 35 opens the circuit for restoring busy relay 60, and at contacts 48 closes the following circuit .of the release magnet: ground, contacts 22, contacts 33, contacts 48, contacts 94, release magnet RLSE, and negative battery. The shaft and wipers 213 to 216 inclusive are restored to normal and the off-normal spring VON is actuated to open the circuit of the release magnet and to close the following circuit for homing the cams of sequence switch SEQ: ground, contacts 22, contacts 33, contacts 48, contacts 93, contacts I20, interrupter contacts 31, stepping magnet SM, and negative battery. The magnet SM interrupts its own circuit repeatedly at contacts 31 to advance the cams from position 3 to normal position I. Cam CI at contacts I20 disconnects ground from the interrupter springs, and at contacts I2I makes the switch ready for another call by connecting negative potential through resistor R, contacts I2I, contacts 13, and contacts 36 to control conductor C.

If the last line of the group is idle as wipers 213 to 216 inclusive engage the bank contacts corresponding to this line, wiper 215 does not encounter ground on contact 282 for completing the circuit of busy relay 50 and it releases. At contacts 6| a circuit is prepared for placing ground On wiper 2'. 5; and at contacts 64 a circuit is prepared for energizing the sequence magnet SM; As in the previous description for a busy condition relay 513 releases shortly after the completion of rotary motion, but now at contacts 52 the following circuit is closed to energize magnet SM: ground, contacts 35, contacts 64, contacts 52, contacts H4, contacts I34, contacts 31 of the interrupter springs, magnet SM, and negative battery. Upon operating, the magnet interrupts its circuit and. then releases to advance the cams to position 4. Cam C1 at contacts I36 and I39 prepares circuits required when the night service feature is used, at contacts I31 opens a point in the extra control circuit, and at contacts I38 places ground on wiper 215 for operating the cutoff relay 2 50 in the subscribers line equipment. The cams of the sequence switch continue to position 5. Cam 05 at contacts I34 opens the operating circuit of magnet SM, and at contacts I35 opens an additional point in the circuit of the rotary magnet. Cam C3 at contacts I25 and I26 connects interrupted ringing current from the ringing machine GEN to the wanted subscribers lines, at contacts I21 completes the circuit for returning ring-back-tone to the calling subscriber, and at contacts I28 closes a circuit for advancing the cams of the sequence switch at fixed intervals. The circuit for periodically energizing Upon recogniz the sequence switch magnet includes ground, an interrupter (not shown) which may be controlled by the ringing generator or a timing device, lead marked GRD. PULSE, contacts 46, contacts =83, contacts I28, contacts I29, winding of magnet SM, and negative battery.

If the called subscriber does not answer immediately the cams continue to position 8, and cams C4 at contacts I29 opens the operating circuit of magnet SM, at contacts I30 prepares another circuit for magnet SM, at contacts I3I completes a locking circuit for relay 4a, and at contacts I32 completes the following circuit to sound an alarm for notifying a maintainer: ground, contacts I5, contacts llI, contacts 532, and to alarm equipment.

After the alarm sounds, should the calling subscriber hang up before the call is answered, the connector still remains in the ringing position until a maintainer finds the fault, or 21 called subscriber or an operator at the private branch exchange answers. When the subscriber hangs up, relay 2G releases and opens the circuit of slow releasing relay 39 at contacts 2 I. Relay 38 at contacts 3| opens the initial operating circuit of relay 4!], and at contacts 34 removes ground from control conductor C to release the preceding switches. The circuit which ordinarily releases the connector is open at contact 88 of relay 48; relay 4B is maintained operated by the locking circuit including ground, contacts I3I, contacts 96, contacts 44, Winding of relay 4D, and negative battery.

If the called subscriber or operator answers in response to the ringing which continues after the calling subscriber has hung up, the following circuit is completed for operating the ringcut-off relay 86: negative battery at ringing generator GEN, upper winding of relay 80, contacts 85, contacts 45, contacts I26, wiper 213, over the subscribers loop to wiper 214, contacts I25, contacts 49, contacts 89, and ground. Relay 8!) at contacts 96 opens the locking circuit of relay 46. The circuit for releasing the connector is completed at contacts 48, and the connector restores to normal in the manner previousl described.

Should the called subscriber or operator answer when the cams of the sequence switch are in position 8 and the calling subscriber is still waiting for an answer, the circuit as previously contacts 96 opens the locking circuit of relay d6 to transfer control of the release magnet back to the calling subscriber, at contacts 84 closes a circuit to the sequence switch magnet, at contacts 85 and 89 disconnects the called subscribers lines from the circuit of the ring-cut-off relay, at contacts 8'5 and 88 connects th lines to the backbridge relay I6 and also tothe calling subscribers lines through condensers c1 and 98, and at contacts 95 completes its locking circuit through contacts 35 controlled by relay 4!]. The circuit for energizing the sequence magnet may be traced from the lead marked GRD. PULSE, contacts 46, contacts 84, contacts I30, and winding of sequence magnet SM to negative battery. Upon advancing to position 9, cam 04 at contacts I36 opens a point in the operating circuit of magnet SM. The circuit for operating back bridge relay It] includes ground, lower winding of relay Ill, contacts 88, contacts 49, contacts I25, wiper 214, the subscribors loop to wipers 213, contacts I26, contacts 45,

8 l contacts =86, upper winding of relay l0, and negative battery. At armatures I2 and I3 the current flow is reversed to the calling subscriberslines. When the conversation is completed and the calling subscriber hangs up, the connector is released as previously described.

Normally, the called subscriber or operator answers before an alarm sounds. When ring-cute ofi relay operates in response to answering before the cams reach position 8, the circuit of the sequence switch magnet SM is opened at contacts 83 to stop the cams.

When the night service feature is employed, the connector responds to an additional digit. In response to the first digit that is dialed as usual after the connector is seized, the wipers 213 to 216 are raised to the desired level and the cams CI to Cl inclusive are advanced to position 2 in the manner previously described. A particular digit such as digit 1 is then dialed to cause relay I ID to operate. In response to the single impulse corresponding to digit 1 the rotary magnet is operated over the previously traced circuit from ground, contacts 22, contacts 32, contacts I33, contacts I23, and Winding of magnet ROT to negative battery; relay I0 operates over the circuit including ground, contacts 22, contacts 32, contacts I33, winding of relay 16, and negative battery. The wipers are rotated to the contacts in the first position of the banks. The contacts engaged by wipers 213, 214, and 215 are not connected; but EC contact 211 engaged by wiper 216 is connected permanently to ground. Shortly after the impulse, relay I6 releases, at contacts II closes the circuit for operating relay I I0, and at contacts I2 opens the circuit of magnet SM. At contacts H2 a locking circuit is completed from ground, contacts 43, contacts H2, and winding of relay II I] to negative battery; at contacts II3 the operating circuit of relay IIo is opened; at contacts l I6 pulsing circuits are prepared for relay 55 and the rotary magnet; at contacts II5 a circuit is prepared for relay I0; and at contacts III the operating circuit of stepping relay is opened to prevent automatic rotary when a subsequently tested called line tests busy. When the magnet SM releases, the cams of the sequence switch are advanced to position 3. Cam C5 opens contacts I33, but the circuit is still prepared to relay 16 through contacts I36 and contacts Il5. Cam 06 at contacts I35 connects the rotary magnet to the pulsing circuit.

After the automatic rotary has been rendered ineffective, the final digit is dialed for connecting the wipers to the desired line. The number of impulses to be sent is one less than the total number of rotary steps required to engage the desired contacts. The ordinary dial that sends a maximum of ten impulses in a series can be used to rotate the wipers to a line connected to the eleventh set of contacts in the bank. The circuit for the rotary magnet may be traced from ground, contacts 22, contacts 32, contacts I36, contacts H6, contacts I35, and winding of rotary magnet EDT to the negative battery. The fol--' lowing circuit is completed for operating slow releasing relay 50: ground, contacts v22, contacts 32, contacts I36, contacts H6, relay 5!], and negative battery. Relay To is operated over the circuit including contacts 22, contacts 32, contacts I36, contacts H5, and relay I0. At contacts "I2 the circuit is completed for energizing magnet SM.

If the line is busy, relay 60 operates to return busy signal. When the calling subscriber hangs 539 up," the connector releases 'as described for busy c'ondition'on thelast line of a group. I

Whentheline is idle, relay 6U is not operated as relay 50 and relay Ill release. MagnetSM re"- leases to advancethecams of the sequence switch to position l, CamjCI at contacts I36 opens a point in the pulsing circuitjat contacts I38connects ground potential towi per 215 to operate the called subscribers cut-off relay, and at contacts I39 closes a circuit for advancing the cams to position 5. The circuit. for "advancing the cams includes ground, contacts 35 contacts 64, contacts 52, contacts I39, contacts I34, inter rupter springs 31, magnet SM, and negative battery. Cam C6 at contacts? I35 disconnectsthe rotary magnet from the pulsing circuit, and at contacts I34 opens the circuit to the interrupter springs of the sequence magnet. Cam C3 at contacts I28 connects the sequence magnet SM to the interrupter supplying timed ground pulses, at contacts I2! connects ring-back-tone to the calling subscribers lines, and at contacts I25 and I26 connects'the called subscribers line to the ringing circuit. Theconnection iscompleted as previously described' After the conversation, is over, the switch releases in the usual manner. Relay H is released when its locking circuit is opened at contacts 43 of relay 4!].

Although the present invention has been embodied in a specific structure, extensive departures in the embodiment may be made without departing from the scope and spirit of the invention.

What is claimed is: 1' 1. In a telephone system, a calling line, a called line, a sequence switch, means under the control of said calling line for connecting said switch to said called line, means for operating saidswitch to connect a ringing generator to said called line, means for advancing said switch at a predetermined rate to measure an interval of time after the connection of ringing generator to said called line, an alarm circuit, and means'in said switch at the end of said time interval for closing said alarm circuit.

2. In a telephone system,"ca1ling and called lines, an automatic two motion connector switch controlled from a calling subscriber to step in both of its motions to a position corresponding to a called line, a source of signalling current, a cam controlled sequence switch operated one step at a time throughoutthe movements of the con-. nector switch to controlboth movements thereof and to connect said source of signalling current to the called line after the position is reached, and means for thereafter operating said sequence switch as a timing switch, an alarm signal, said sequence switch being effective to control said alarm signal after a predetermined time to indicate an unanswered call.

3. In a telephone system, a calling line, a called line, a connector having access to said called line, means controlled from said calling line for operating said connector to engage said called line, means for applying ringing currentto said called line and for measuring a predetermined time, a restoring means under the control of said calling line prior to the completion of said predetermined time for restoring said connector, means effective at the end of said predetermined time to sound an alarm and to render said restoring means independent of control from said calling line, and means effective thereafter for controlling said restoring means from said called line.

4. In a telephone system, a calling line, a called "ill line, a connector, a timing device, means 'simul taneously efiective for operating said connector to engage" said calledlineand for starting said timing device to measure a predetermined time, a restoring means, means'under the control er said calling line for operating said restoring means to restore said connector, means effective at the end of said predetermined time for removing control of saidlrestoringmeans from said calling line, and means under the control of said called linefor returning control of said restoring means to said calling line.

5; In a telephone system, 9. called line, a calling line, a connector having wipers accessible to contacts of said called line, means under thecon v trol of said calling linefor engaging said wipers with said contacts, means for applying ringing current to said called line and for measuring a predetermined time, a restoring means, means under th'e, control ol? said calling line for operating said restoring means prior to thecomple tion of said predetermined time, means'efiective at the end of said predetermined time if the restoring means has not operated to render said restoring means independent of control from said calling line and to sound an alarm, and means thereafter under the control of said called line for operating said restoring means to restore said wipers. j

, 6. In a telephone system, a group of, li'nesj a connector having access to said group of lines", means directively controlled from a calling line for operating said connector to select an idle line of said group, means effective in case the con;- nector engages a busy linefor operating said connector automatically to select an idle remain; ing line in saidgroup, a night contact assigned to said group of lines, means operative in case the connector, has been operated to select said nightcontact' for preventing automatic operation ofsaid connector to. select an idle line, and means in said connector responsive to asubse quent digit for operating said connector from said night contact to. a position corresponding to another .line of said group regardless of its idle or busy condition.

'7. In a telephone system, a connector, a plu rality of groups of lines and a control circuit connection accessible to said connector, a calling line, means directively controlled from said calling line for operating said connector to select any one of said lines or to select said control circuit connection, means operative in the first instance if a busy one of said lines of a group is encountered for operating said connector to find an idle remaining line in the group, means operated when the control circuit is selected for preventing the automatic operation of said connector during the subsequent selection of a line in any of said groups, and means directively controlled from said calling line for operating said connector to select any one of said lines regardless of its idle or busy condition.

8. In a telephone system, calling and called lines, a connector switch controlled from a calling line to connect with and test said called lines, certain of said called lines arranged in groups in the bank of said switch, said connector switch operated in response to a single digit dialed by a calling subscriber to move to a position corresponding to the first line of a group and if that line is busy to step to the positions of other I lines of the group until an idle one is found, an-

1:1 switch is operated'to said other Position for preventing further automatic operation of the switch but permitting directive operation thereof in re sponse to a second digit dialed by the calling subscriber to seize and test any particular one of the lines of the group whether busy or idle and to return a busy signal ,in-case the particular line selected is busy.

9. In a telephone system, an automatic switch, a control wiper and an extracontrol wiper thereior, sets of contacts accessible to said wipers, a busy relay, a stepping relay, means for operating said switch to engage one of said sets of contacts, a circuit including said control wiper for operatingsaid busy relay in case said control wiper encounters a ground potential on the contact enaged thereby, a circuit completed by the operation of said busy relay to connect said stepping .relay to said extra control wiper, said circuit of the stepping relay effective in case said extracom trol wiper encounters ground potential on the contact engaged thereby for operating said step ping relay, means controlled by said step-ping relay for stepping said wipers, a third relay, a circuit for said third relay including said extracon- .trol wiper, said .circuit of the third relay effective in case said extra control wiper alone encounters a ground potential on .a contact of one of. said sets for operating said third relay, and contacts included in said circuit of the stepping relay opened in response .to the operation of said third relay.

10, In .a telephone system, a group of lines, a set .of contacts for each line, each set including a control contact and an extra control contact, an automatic switch having access to said sets, a line relay and a cut-cit relay vfor each of said lines, means for connecting a busy potential to the control contact of the first -line ,in said group, multiple circuits including contacts on said lin relays and onrsaid cut-off relays Ior connecting said busy potential to the extra control contact of said first line, means for operating said switch to select the set of contacts of said first line, means responsive to the finding of busy potential .on both the control contact and extra control contact for operating said switch to test other ones of said lines, and means efiective if all the lines of said group are busy for operating the line relay or the cut-cit relay of each of said lines, said operated relays removing said busy potential from the extra control contact of said first line to prevent said switch from testing other busy lines.

11. In a telephone system, a group of lines, a control contact and an extra controlcontact for the first line of said group, an'automatic switch having access to said lines, means for connecting a busy potential to .said control contact, a line relay and a cut-.ofi relay for each of said lines, multiple circuits controlled by said relays except the line relay and cut-off relay .of the first line .of said roup, said multiple circuits connecting said busy potential to said extra control contacts, means for operating said switch to select said first line, means responsive to encountering said busy potential on both of said contacts for operating said switch to test other ones of said lines, and means effective if all of said lines are busy for operating the line relay or the cut-ofi relay of each .of said lines,said operated relays of said lines except said first line removing said busy potential from said extra control contacts to prevent said switch from testing other lines of said CLARENCE LOMAX.

REFERENCES CITE-D Thefollowing references are .of record in, the file of this patent;

UNITED STATES PATENTS 

